title: Pharmacological insights from P-glycoprotein knockout mice.
abstract: The mdr1-type P-glycoproteins can confer multidrug resistance to tumor cells by actively pumping a wide variety of drugs from the cell. To counteract this drug resistance, P-glycocoprotein-blocking agents are currently administered to patients during chemotherapy. However, this may also affect the normal physiological function(s) of the mdr1-type P-glycocoproteins. In order to establish these functions, we have generated mice with a genetic deficiency in both of their mdr1-type P-glycocoprotein genes. Our results indicate the mdr1-type P-glycocoproteins are not essential for basic physiological functions. However, mice without mdr1-type P-glycocoproteins display drastic alterations in the pharmacological handling of drugs, demonstrating an important role for mdr1-type P-glycocoprotein in the blood-brain barrier, where it prevents the accumulation of many drugs in the brain. Moreover, we found that intestinal P-glycocoprotein has a prominent role in the extrusion of several drugs from the blood into the intestinal lumen, and in preventing drugs in the intestinal lumen from (re-)entering the bloodstream. The latter property can have important implications for the oral bioavailability of many drugs. Our results indicate that effective P-glycocoprotein-blocking agents should be used with caution, given the potentially extensive pharmacokinetic effects of treatment with these compounds.
authors.affiliation: Division of Experimental Therapy, Netherlands Cancer Institute, Amsterdam, The Netherlands.
authors.forename: A H
authors.initials: AH
authors.lastname: Schinkel
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D018432:Drug Resistance, Multiple / Q000235:genetics*; D019450:Genes, MDR; D051379:Mice; D018345:Mice, Knockout / Q000235:genetics*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1